hash_update

(PHP 5 >= 5.1.2, PECL hash >= 1.1)

hash_update — Pump data into an active hashing context

说明

bool hash_update ( resource $context , string $data )

参数

context: Hashing context returned by hash_init().
data: Message to be included in the hash digest.

返回值

Returns TRUE.

参见

hash_init() - Initialize an incremental hashing context
hash_update_file() - Pump data into an active hashing context from a file
hash_update_stream() - Pump data into an active hashing context from an open stream
hash_final() - Finalize an incremental hash and return resulting digest

PHP手册 - N: Pump data into an active hashing context

用户评论:

Dainichi (25-Jul-2006 02:19)

A simple example on incremental file hashing: $fp = fopen($file, "r"); $ctx = hash_init('sha256'); while (!feof($fp)) { $buffer = fgets($fp, 65536); hash_update($ctx, $buffer); } $hash = hash_final($ctx, true); fclose($fp); While incremental hashing is quite slow, it's the easiest way to hash - parts of large files: I.e., a 700MB avi video uses first x bytes to store metadata, so in order to hash the avi's data only, you have to fseek to data start and use incremental hashing - streaming data if php just proxies the data - whenever it's inadequate or impossible to store the data being hashed into memory (i.e. because of their size) or on disc.